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Change a Charts Series (or Data) from a different thread


noizwaves
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 Hi,

I'm writing an application that changes the data in a ChartFX chart from another thread. It removes the series from the chart, then adds some new ones. These operations are called from a thread that did not create the chart. Currently i'm using this code to add a series to the chart:

  private delegate void ChartSeriesAddSafeHandler(Chart ch, SeriesAttributes s);   public static void ChartSeriesAddSafe(this Chart ch, SeriesAttributes s)   {   if (ch.Dispatcher.Thread == Thread.CurrentThread)   {   ch.Series.Add(s);   }   else   {   ch.Dispatcher.Invoke(System.Windows.Threading.DispatcherPriority.Send, new ChartSeriesAddSafeHandler(ChartSeriesAddSafe), ch,s);   }   }

 

Using similar code to above, i'm able to set a chart's item source, clear the series, and set a series itemsource. However, adding a series to a chart fails with this exception:

Exception has been thrown by the target of an invocation.The calling thread cannot access this object because a different thread owns it.

I suspect theres some code inside of the chart object that isn't threadsafe. Any recommendations on how to get this working?

post-2982-13922406276261_thumb.gif

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It is my understanding that in WPF (not just ChartFX) only the thread that creates a UI object can access it.  I ran into a similar problem with some other code, and this is the response I received.  Unfortunately I can't find a link at the moment that explicitly states this, sorry. 

You can look at using Control.Dispatcher.Invoke or BeginInvoke to try to get your code working.  However, In my case, I ended up doing all of the non-UI calculations in a separate thread and then passing the data to the main thread to get my UI objects created. 

If I can find the right links, I'll post them.  Sorry I couldn't be of more help.  I just wanted to let you know that based on my experience with this issue I don't believe ChartFX is the root of the problem and that the WPF is responsible.  That isn't to say that ChartFX may not have a workaround for it. :D

Dave

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SeriesAttributes derives from DispatcherObject which gives it thread-affinity. The reason why SeriesAttributes derive from this class is that in order to allow you to create bindings between your UI and a Series it has to be either a FrameworkElement or a FrameworkContentElement.

I would recommend (as Dave did) you do your calculations/data retrieval on a different thread but then pass the data (and create additional series) on your UI thread.

If you can create a sample application that shows ChartFX not handling this correctly please send it to us.

Regards,

JuanC

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 Thanks Davidam and JuanC,

I realised my misdirection with my previous attempts: I was trying to change the properties of the chart from a different thread via Dispatcher.Invoke (one call to Invoke per property to change).

Instead, I needed to be calling Invoke on a method inside my UserControl from the different thread.

If anyone is having similar problems, reply back and ill post some code samples.

 

Adam

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